[diagrams] save attribute names instead of indices (fix #7914)
we don't have a file menu anymore (also moves project properties to project menu on windows)
Add a QgsDebugCall macro to trace entering/leaving functions

Replace manual debugging lines used for the same purpose in a couple
of implementation files for node tool.
Fix leak of geometry in QgsSelectedFeature destructor
Update QgsDataDefinedButton

- Add 'Usage info' functions; displays in description and tool tip
- Reorganize menu, adding conceptual section titles
- Add ability to paste in expression
- Add ability to clear defined expression
- Add check for non-matching data field types
- Add better truncation of expressions in tool tip and menu